JP3511021B2 - Switching power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device, and more particularly to a switching power supply device suitable for driving a load whose load current can fluctuate rapidly.

[0002]

2. Description of the Related Art So-called DC / DC converters have been known as switching power supply devices. In a typical DC / DC converter, a DC input is once converted into an AC using a switching circuit, then this is transformed (boosted or stepped down) with a transformer, and then this is converted into DC using an output circuit. This is a device for producing a direct current output having a voltage different from the input voltage.

In such a switching power supply device, the output voltage is detected by the control circuit, and the switching operation by the switching circuit is controlled based on the detected output voltage. As a result, a stable operating voltage is supplied to the load to be driven by the switching power supply device.

[0004]

However, when driving a load in which the load current (output current when viewed from the switching power supply device) fluctuates abruptly, the conventional switching power supply device stably holds the output voltage. It was difficult.

In particular, a CPU (Central Processing Unit) and a DSP (Digital Signal Processor) have a low operating voltage and require a large current in an active state, and a small current in an inactive state. Since it is not necessary, in the conventional switching power supply device, there is a possibility that the output voltage fluctuates greatly due to a sudden change in the output current. Moreover, CPU
Since the or DSP is a device that operates at a very high speed, if the output voltage fluctuates, the CPU or the DSP may malfunction if not stabilized quickly.

Therefore, an object of the present invention is to provide a switching power supply device suitable for driving a load whose load current can fluctuate rapidly.

Another object of the present invention is to provide a switching power supply device in which fluctuations in output voltage due to abrupt fluctuations in output current are reduced.

Still another object of the present invention is to provide a switching power supply device equipped with a control circuit capable of promptly recovering the fluctuation of the output voltage caused by the sudden fluctuation of the output current.

An object of the present invention is to provide a main circuit section having a switching circuit for converting a DC input voltage into an AC voltage and an output circuit for rectifying the AC voltage to generate a DC output voltage, and the output. A control circuit that has at least an amplifier that receives a voltage or a voltage that is interlocked therewith and that controls the operation of the main circuit unit; and the load current supplied from the main circuit unit has changed at a speed exceeding a predetermined speed. In response, the switching power supply device is characterized in that it includes means for varying the level of the input terminal of the amplifier.

In a preferred embodiment of the present invention, the level of the input terminal of the amplifier which varies in response to the load current changing at a rate exceeding a predetermined rate is a level at which the output of the amplifier is saturated. is there.

[0011]

In a preferred embodiment of the present invention, the means unidirectionally fluctuates the level at the input end of the amplifier in response to the load current increasing at a rate exceeding the predetermined rate. Reversing the level at the input of the amplifier in response to the load current decreasing at a rate above the predetermined rate.

In a further preferred aspect of the present invention, the means has a first level when the load current changes at a first speed equal to or lower than a predetermined speed, and the load current changes to the predetermined speed. The level of the input terminal of the amplifier is changed so as to become the second level exceeding the first level when changing at the second speed exceeding 0.

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

DETAILED DESCRIPTION OF THE INVENTION Referring to the accompanying drawings,
A preferred embodiment of the present invention will be described in detail.

FIG. 1 is a circuit diagram of a switching power supply device according to a preferred embodiment of the present invention.

As shown in FIG. 1, the switching power supply device according to the present embodiment transforms a DC input voltage Vin supplied to a pair of input terminals 1 and 2 and outputs a pair of output voltage Vo having a predetermined voltage. Is a device that supplies the output terminals 3 and 4 of the above, and includes a main circuit portion 5, a control circuit 6, and a sudden load change detection circuit 7. Although not particularly limited, the pair of output terminals 3 and 4 operate on a low voltage (for example, 1 V) like a CPU or a DSP, but are a power source for a device that requires a large current (for example, 100 A). The terminals are connected. The CPU and DSP require a large amount of current in the active state, but require a small amount of current in the inactive state, and have a characteristic that switching between the active state and the inactive state is extremely fast. And
The switching power supply device according to this embodiment can be suitably used as a power supply for driving a device (load) having such characteristics.

The main circuit section 5 includes a transformer 10, a half-bridge type switching circuit provided on the primary side of the transformer 10, and a current doubler type (double current type) provided on the secondary side of the transformer 10. And an output circuit.

The switching circuit included in the main circuit portion 5 is a first circuit connected in series between a pair of input terminals 1 and 2.
Input capacitor 11 and second input capacitor 12
And a first connected in series between the pair of input terminals 1 and 2
Main switch 13 and second main switch 14
And a driver 15 for driving the first main switch 13
And a driver 16 for driving the second main switch 14.
It has and. As shown in FIG. 1, the first and second
Of the input capacitors 11 and 12 of the
The primary winding of the transformer 10 is connected between the connection points of the main switches 13 and 14. As the first and second main switches 13 and 14, various known elements or circuits can be used.

The output circuit included in the main circuit section 5 includes a first reactor 17 and a first rectifying switch 19 connected in series between a pair of output terminals 3 and 4, and a pair of output terminals 3 and 4. The second reactor 18 and the second rectifying switch 20 connected in series with the pair of output terminals 3 and 4
An output capacitor 21 connected between them, a driver 22 that drives the first rectifying switch 19, and a driver 23 that drives the second rectifying switch 20 are provided. As shown in FIG. 1, the transformer 1 is provided between the connection point between the first reactor 17 and the first rectifying switch 19 and the connection point between the second reactor 18 and the second rectifying switch 20.
0 secondary winding is connected. Further, as the first and second rectifying switches 19 and 20, various known elements or circuits can be used.

The control circuit 6 includes an amplifier 30, a PWM control circuit 31, an insulation circuit 32, and resistors 33 and 34.

The amplifier 30 has an inverting input terminal (-), a non-inverting input terminal (+) and an output terminal, and is provided between the inverting input terminal (-) and one output terminal 3 of the switching power supply device. The resistor 33 is inserted, and the resistor 34 is inserted between the inverting input terminal (−) and the output terminal. Further, the reference voltage Vref is supplied to the non-inverting input terminal (+). As a result, the control signal S1 appearing at the output end of the amplifier 30 changes according to the output voltage Vo appearing at the one output terminal 3. More specifically, the higher the output voltage Vo, the lower the level of the control signal S1 that appears at the output end of the amplifier 30, and conversely, the lower the output voltage Vo, the control signal that appears at the output end of the amplifier 30. The level of S1 rises.

The PWM control circuit 31 receives the control signal S1 supplied from the amplifier 30, and controls the pulse widths of the control signals a and b based on the control signal S1. More specifically, PWM
The control circuit 31 widens the pulse width of these control signals a and b (increases the duty) as the level of the control signal S1 is higher, and conversely, as the level of the control signal S1 is lower, the control signal a is lower. , B to narrow the pulse width (lower the duty). Here, the control signals a and b
Are signals used to control ON / OFF of the first main switch 13 and the second main switch 14, respectively. Further, the PWM control circuit 31 controls the control signals c and d to have appropriate pulse widths according to the pulse widths of the control signals a and b. Here, the control signals c and d are the first rectifying switch 19 and the second rectifying switch 2 respectively.
This is a signal used to control 0 on / off.

The insulating circuit 32 is a circuit for receiving the control signals a and b belonging to the secondary side of the transformer 10 and converting these into control signals A and B belonging to the primary side of the transformer 10, respectively. The insulating circuit 32 is not particularly limited.
As such, a transformer, a photocoupler, or the like can be used.

As shown in FIG. 1, the control signal A is supplied to the driver 15, the control signal B is supplied to the driver 16, the control signal c is supplied to the driver 22, and the control signal d is supplied to the driver 23. It These drivers turn on the corresponding switch when the corresponding control signal becomes active (for example, high level), and turn off the corresponding switch when the corresponding control signal becomes inactive (for example, low level). State.

The sudden load change detection circuit 7 includes a filter 40,
Filter 41, comparator 42, transistor 4
3 and a resistor 35.

The filter 40 includes a pair of output terminals 3 and 4.
It is provided with resistors 44 and 45 connected in series between them and a capacitor 46 connected in parallel to the resistor 45, and the potential at the connection point of the resistors 44 and 45 is the control signal S2.
Used as. Similarly, the filter 41 includes resistors 47 and 48 connected in series between the pair of output terminals 3 and 4.
And a capacitor 49 connected in parallel with the resistor 48.
And the potential at the connection point of the resistors 47 and 48 is used as the control signal S3. With this configuration, the filter 40 functions as a low-pass filter circuit that inputs the output voltage Vo and outputs the control signal S2, and the filter 41 functions as a low-pass filter circuit that inputs the output voltage Vo and outputs the control signal S3. To do.

Here, the characteristics of the filter 40 and the filter 4
The filter characteristics of 1 are different from each other. More specifically, the filter 40 is set to have a larger time constant than the filter 41. Therefore, when the output voltage Vo fluctuates, the filter 41 is better than the filter 40.
Fluctuates more than. Further, when the output voltage Vo is stable and when the output voltage Vo is fluctuating but the degree of the fluctuation is small, the control signal S2 which is the output of the filter 40 is the output of the filter 41. Is set to be lower than the control signal S3. The setting of such characteristics is performed by the filters 40 and 4
1 constituting resistors 44, 45, 47 and 48, and
This can be done by proper selection of the constants of capacitors 46 and 49.

The comparator 42 has an inverting input terminal (-),
It has a non-inverting input terminal (+) and an output terminal. The control signal S2 is supplied to the non-inverting input terminal (+) and the control signal S3 is supplied to the inverting input terminal (-). As a result, when the level of the control signal S2 is lower than the level of the control signal S3, the control signal S4 which is the output of the comparator 42 becomes low level, and conversely, the level of the control signal S2 is lower than the level of the control signal S3. If is also high, the control signal S4, which is the output of the comparator 42, becomes high level. Here, the control signal S4 is used as a sudden load change detection signal.

Although not particularly limited, the transistor 43 is composed of an NPN type bipolar transistor, and the control signal S4 is supplied to its base. Also,
The emitter of the transistor 43 is connected to the output terminal 4 (GND), and the collector of the transistor 43 is a resistor 3
It is connected to the inverting input terminal (−) of the amplifier 30 via 5.

Next, the operation of the switching power supply according to this embodiment in the sudden load change state will be described.
In the present specification, the “load sudden change state” refers to a state in which the output current Io changes rapidly.

FIG. 2 is a timing chart showing the operation of the switching power supply according to this embodiment in the sudden load change state.

FIG. 2 shows the operation of the switching power supply device when the amount of the output current Io sharply increases from the time t0 to the time t2, which is, for example, a pair of output terminals 3 and 4. When the load connected to the CPU is a CPU or a DSP, such a phenomenon occurs when the CPU or the DSP is switched from the inactive state to the active state.

First, before the time t0, the output voltage Vo is kept at the target voltage because the amount of the output current Io is small and there is almost no fluctuation. In this case, the control signal S2 output from the filter 40 has a lower level than the control signal S3 output from the filter 41, and thus the control signal S4 output from the comparator 42 maintains a low level. As a result, the transistor 43 is turned off, and the control signal S5 is in a high impedance state when viewed from the inverting input terminal (-) of the amplifier 30. Therefore, before the time t0, the sudden load change detection circuit 7 does not substantially affect the operation of the control circuit 6. In this case, the transfer function of the control circuit 6 has the first value, and the transfer function of the closed loop including the main circuit unit 5 and the control circuit 6 is suppressed to a value at which the output voltage Vo does not oscillate.

Next, when the output current Io starts to increase rapidly at time t0, the output voltage Vo starts to decrease rapidly. When the output voltage Vo drops sharply,
The filter 40 receiving this lowers the level of the output control signal S2, and the filter 41 lowers the level of the output control signal S3. In this case, the control signal S3, which is the output of the filter 41, is set to vary more greatly than the control signal S2, which is the output of the filter 40, with respect to the variation of the output voltage Vo. At t1, the magnitude relationship between the levels of the control signal S2 and the control signal S3 is reversed. That is, the control signal S2 has a higher level than the control signal S3.

As a result, the control signal S4, which is the output of the comparator 42, becomes high level, and the transistor 43
Turns on. When the transistor 43 is turned on, the level of the control signal S5 becomes the potential (ground potential) of the output terminal 4 (GND). Therefore, the inverting input terminal (−) of the amplifier 30 is grounded via the resistor 35. Is supplied.

As a result, the level of the control signal S1 which is the output of the amplifier 30 rises rapidly, and typically rises to the saturation level. Therefore, P that receives the control signal S1
The WM control circuit 31 substantially expands the pulse width of the output control signals a and b to the maximum value, whereby the lowered level of the output voltage Vo rapidly rises toward the target voltage. start. In such a state, the transfer function of the control circuit 6 has a second value exceeding the first value.
In this case, the transfer function of the closed loop including the main circuit unit 5 and the control circuit 6 may be at a level at which the output voltage Vo oscillates. Such a state is maintained until the magnitude relationship between the levels of the control signal S2 and the control signal S3 is reversed again, that is, the control signal S2 becomes lower than the control signal S3.

When the control signal S2 becomes lower than the control signal S3 at time t3, the control signal S4 output from the comparator 42 returns to low level, and the transistor 43 is turned off again. As a result, the sudden load change detection circuit 7 does not substantially affect the operation of the control circuit 6. Then, at time t4, the level of the output voltage Vo returns to the target voltage, and the level of the control signal S1 is also stabilized.

By the above operation, in the switching power supply device according to the present embodiment, the rapid decrease in the output voltage Vo due to the sudden change in the load state can be quickly recovered, so that the transient response is greatly improved.

In FIG. 2, the waveform of the output voltage Vo and the waveform of the control signal S1 when the load sudden change detection circuit 7 is removed from the switching power supply device according to this embodiment are shown as Vo 'and S1', respectively. Has been done. As is apparent from FIG. 2, if the sudden load change detection circuit 7 is removed from the switching power supply device according to the present embodiment, even if the output voltage Vo drops rapidly due to a sudden change in the load state, the control signal S
Since the increase of 1 is gradual, it takes a long time for the level of the output voltage Vo to return to the target voltage.
In this example, the level of the output voltage Vo returns to the target voltage at time t5, and the level of the control signal S1 is also in a stable state.

Therefore, in the switching power supply device according to the present embodiment, when the output voltage Vo rapidly decreases due to a sudden change in the load state, as compared with the case where the sudden load change detection circuit 7 is not provided, the time t5 to the time t4. It is possible to restore the level of the output voltage Vo to the target voltage as early as the given time.

Next, the operation of the switching power supply device according to this embodiment in the normal state will be described. still,
In the present specification, the “normal state” refers to a state in which the output current Io is stable or fluctuates even if it fluctuates, that is, a state other than the sudden load change state.

FIG. 3 is a timing chart showing the operation of the switching power supply device according to this embodiment in the normal state. FIG. 3 shows the operation of the switching power supply device when the amount of the output current Io increases relatively gently between the time t6 and the time t7 (time t7-time t6> time t2-time t0). .

In this way, when the amount of the output current Io increases relatively slowly, the output voltage V associated with this increases.
The decrease of o is gentle, and the control signal S2 and the control signal S
There is no reversal of the magnitude relationship between the 3 levels. Therefore, the control signal S4, which is the output of the comparator 42, maintains the low level, and the transistor 43 maintains the off state. As described above, when the transistor 43 is in the off state, the sudden load change detection circuit 7 does not substantially affect the operation of the control circuit 6. Therefore, the switching power supply device according to the present embodiment can perform normal operation in the normal state.

As described above, in the switching power supply device according to this embodiment, a rapid drop in the output voltage Vo due to a sudden change in the load state can be quickly recovered, so that, for example, a CPU or a DSP as a load can be recovered.
Even when driving, the malfunctions due to the fluctuation of the power supply voltage can be effectively prevented.

Further, in the switching power supply device according to this embodiment, the filters 40 and 4 having a function as a low-pass filter for detecting a sudden load change state.
Since 1 is used, it is possible to prevent a malfunction caused by erroneously recognizing a ripple voltage fluctuation generated due to the switching operation of the main circuit unit 5 as a sudden load change state.

Further, according to the switching power supply device of the present embodiment, the sudden change in load is indirectly detected by monitoring the output voltage Vo. Therefore, the output current Io is detected by using a resistor or a current transformer. There is no power loss or operation delay that occurs when the direct detection is performed. Therefore, the output capacitor 21 of the switching power supply device is arranged in the vicinity of the load which is arranged relatively far from the main body of the switching power supply device, and the detection point of the output voltage Vo is in the vicinity of the load. It is possible to provide a switching power supply device suitable for performing the above.

As a method for promptly recovering the rapid decrease in the output voltage Vo due to a sudden change in the load state, a method of using a larger-capacity capacitor as the output capacitor 21 can be considered, but in this case, the entire switching power supply device is used. In addition to increasing the size, the cost is increased. On the other hand, in the switching power supply device according to the present embodiment, a rapid decrease in the output voltage Vo due to a sudden change in the load state is promptly suppressed while effectively suppressing such an increase in size of the entire device and an increase in cost. Can be restored to.

Next, another preferred embodiment of the present invention will be described.

FIG. 4 is a circuit diagram of a switching power supply device according to another preferred embodiment of the present invention.

As shown in FIG. 4, the switching power supply device according to this embodiment is different from the switching power supply device shown in FIG. 1 in that the sudden load change detection circuit 7 is replaced by the sudden load change detection circuit 50. different. Since other configurations are similar to those of the switching power supply device shown in FIG. 1, duplicated description will be omitted.

The sudden load change detection circuit 50 includes a filter 41.
, A filter 51, a comparator 52, a transistor 53, and a resistor 54.

The filter 51 includes a pair of output terminals 3 and 4
It is provided with resistors 55 and 56 connected in series between them and a capacitor 57 connected in parallel to the resistor 56, and the potential at the connection point of the resistors 55 and 56 is the control signal S6.
Used as. With this configuration, the filter 51
Functions as a low-pass filter circuit that receives the output voltage Vo and outputs the control signal S6. The circuit configuration of the filter 41 and its function are as described above.

Here, the characteristics of the filter 41 and the filter 5
The filter characteristics of 1 are different from each other. More specifically, more specifically, the filter 41 is the filter 51.
The time constant is set to be larger than that. Therefore, when the output voltage Vo changes, the filter 51 changes more greatly than the filter 41. Further, when the output voltage Vo is stable, and when the output voltage Vo is fluctuating but the degree of the fluctuation is small, the control signal S6 which is the output of the filter 51 is the output of the filter 41. Is set to be lower than the control signal S3. The setting of such characteristics is
Resistors 47, 48, 55 forming filters 41 and 51
And 56 and the constants of capacitors 49 and 57.

The comparator 52 has an inverting input terminal (-),
It has a non-inverting input terminal (+) and an output terminal, the control signal S3 is supplied to the non-inverting input terminal (+), and the control signal S6 is supplied to the inverting input terminal (-). As a result, when the level of the control signal S6 is lower than the level of the control signal S3, the control signal S7 which is the output of the comparator 52 becomes the high level, and conversely, the level of the control signal S6 is higher than the level of the control signal S3. When is also high, the control signal S7, which is the output of the comparator 52, becomes low level. Here, the control signal S7 is used as a sudden load change detection signal.

Although not particularly limited, the transistor 53 is a PNP type bipolar transistor, and the control signal S7 is supplied to its base. Also,
The emitter of the transistor 53 is connected to the output terminal 3 (Vo) , and the collector of the transistor 53 is the resistor 54.
Is connected to the inverting input terminal (−) of the amplifier 30 via.

Next, the operation of the switching power supply according to this embodiment in the sudden load change state will be described.

FIG. 5 is a timing chart showing the operation of the switching power supply according to the present embodiment in the sudden load change state.

FIG. 5 shows the operation of the switching power supply device when the amount of the output current Io sharply decreases from time t10 to time t12, which is, for example, a pair of output terminals 3 and 4. Load connected to CP
In the case of U or DSP, such a phenomenon occurs when the CPU or DSP is switched from the active state to the inactive state.

First, before the time t10, the amount of the output current Io is large, and there is almost no fluctuation, so that the output voltage Vo maintains the target voltage. In this case, the control signal S6 output from the filter 51 is
Since the output level of the control signal S3 is lower than that of the control signal S3 output from the filter 41, the control signal S7 output from the comparator 52 maintains a high level. As a result, the transistor 53 is turned off, and the control signal S8 is in a high impedance state when viewed from the inverting input terminal (-) of the amplifier 30. Therefore, before time t10,
The sudden load change detection circuit 50 does not substantially affect the operation of the control circuit 6. In this case, the transfer function of the control circuit 6 has the first value, and the transfer function of the closed loop including the main circuit unit 5 and the control circuit 6 is suppressed to a value at which the output voltage Vo does not oscillate.

Next, at time t10, when the output current Io starts to decrease sharply, the output voltage Vo starts to increase rapidly. When the output voltage Vo rapidly rises, the filter 41 that receives it raises the level of the output control signal S3, and the filter 51 raises the level of the output control signal S6. In this case, the control signal S6, which is the output of the filter 51, is set to vary more greatly than the control signal S3, which is the output of the filter 41, with respect to the variation of the output voltage Vo. At t11, the magnitude relationship between the levels of the control signal S3 and the control signal S6 is reversed. That is, the control signal S6 has a higher level than the control signal S3.

As a result, the control signal S7, which is the output of the comparator 52, becomes low level, and the transistor 53
Turns on. When the transistor 53 is turned on, the level of the control signal S8 becomes the potential (power supply potential) of the output terminal 3 (Vo) , so that the inverting input terminal (-) of the amplifier 30 is connected to the power supply potential via the resistor 54. Is supplied.

As a result, the level of the control signal S1 which is the output of the amplifier 30 rapidly decreases, typically to the minimum level. Therefore, P that receives the control signal S1
The WM control circuit 31 narrows the pulse width of the output control signals a and b to a substantially minimum value, whereby the level of the output voltage Vo that has risen drops rapidly toward the target voltage. start. In such a state, the transfer function of the control circuit 6 has a second value exceeding the first value.
In this case, the transfer function of the closed loop including the main circuit unit 5 and the control circuit 6 may be at a level at which the output voltage Vo oscillates. Such a state is maintained until the magnitude relationship between the levels of the control signal S3 and the control signal S6 is reversed again, that is, the control signal S6 becomes lower than the control signal S3.

Then, at time t13, the control signal S6
When the signal becomes lower than the control signal S3, the control signal S7 output from the comparator 52 returns to the high level, and the transistor 53 is turned off again. As a result, the sudden load change detection circuit 50 does not substantially affect the operation of the control circuit 6. After that, time t1
At 4, the level of the output voltage Vo returns to the target voltage,
As a result, the level of the control signal S1 also becomes stable.

With the above operation, in the switching power supply device according to the present embodiment, the rapid rise of the output voltage Vo due to the sudden change of the load state can be promptly recovered, so that the transient response is greatly improved.

In FIG. 5, the waveform of the output voltage Vo and the waveform of the control signal S1 when the load sudden change detection circuit 50 is removed from the switching power supply device according to this embodiment are shown as Vo 'and S1', respectively. Has been done. As is apparent from FIG. 5, when the load sudden change detection circuit 50 is deleted from the switching power supply according to the present embodiment, the control signal S1 is gradually decreased even if the output voltage Vo rapidly rises due to the sudden change of the load state. Therefore, it takes a long time for the level of the output voltage Vo to return to the target voltage. In this example, at time t15, the output voltage Vo
Of the control signal S1 returns to the target voltage.
The level of is also in a stable state.

Therefore, in the switching power supply according to the present embodiment, when the output voltage Vo rises rapidly due to a sudden change in the load state, as compared with the case where the sudden load change detection circuit 50 is not provided, the time t15 to the time t14. It is possible to restore the level of the output voltage Vo to the target voltage as early as the given time.

Next, the operation of the switching power supply device according to this embodiment in the normal state will be described.

FIG. 6 is a timing chart showing the operation of the switching power supply according to this embodiment in the normal state. In FIG. 6, from time t16 to time t17 (time t1
7-time t16> time t12-time t10), the operation of the switching power supply device when the amount of the output current Io decreases relatively gently is shown.

In this way, when the amount of the output current Io decreases relatively gently, the output voltage V that accompanies this decreases.
The rise of o is also gentle, and the control signal S3 and the control signal S
The magnitude relationship of the 6 levels will not be reversed. Therefore, the control signal S7, which is the output of the comparator 52, maintains the high level, and the transistor 53 maintains the off state. As described above, when the transistor 53 is in the off state, the sudden load change detection circuit 50 does not substantially affect the operation of the control circuit 6. Therefore, the switching power supply device according to the present embodiment can perform normal operation in the normal state.

As described above, in the switching power supply device according to the present embodiment, a rapid increase in the output voltage Vo due to a sudden change in the load state can be quickly recovered, so that, for example, a CPU or a DSP as a load can be used.
Even when driving, the malfunctions due to the fluctuation of the power supply voltage can be effectively prevented.

Next, another preferred embodiment of the present invention will be described.

FIG. 7 is a circuit diagram of a switching power supply device according to still another preferred embodiment of the present invention.

As shown in FIG. 7, the switching power supply device according to this embodiment is different from the switching power supply device shown in FIG. 1 in that the sudden load change detection circuit 7 is replaced by the sudden load change detection circuit 60. different. Since other configurations are similar to those of the switching power supply device shown in FIG. 1, duplicated description will be omitted.

The sudden load change detection circuit 60 includes a filter 40.
, Filter 41, filter 51, and comparator 4
2, a comparator 52, a transistor 43, a transistor 53, and resistors 35 and 54.

The circuit configurations of the filters 40, 41 and 51 are as described above, and the control signals S3, S2 and S respectively.
6 is generated. Further, the comparators 42 and 51 also receive the corresponding control signals as described above, and generate the control signals S4 and S7 based on the control signals, respectively. Further, the control signal S4 is also supplied to the base of the transistor 43 as described above, and the collector thereof is connected to the inverting input terminal (−) of the amplifier 30 via the resistor 35.
Similarly, the control signal S7 is supplied to the base of the transistor 53, and the collector of the transistor 53 is connected to the inverting input terminal (−) of the amplifier 30 via the resistor 54.

Further, as described above, the filter 40 is set to have a larger time constant than the filter 41, and the filter 41 is set to have a larger time constant than the filter 51. ing. Therefore, when the output voltage Vo changes, the filter 41 changes more than the filter 40, and the filter 51 changes.
Changes more greatly than the filter 41. Furthermore, when the output voltage Vo is stable, and when the output voltage Vo is
Is fluctuating but the degree of the fluctuation is small, the control signal S2 output from the filter 40 is set to have a lower level than the control signal S3 output from the filter 41. Moreover, the control signal S6 output from the filter 51 is set to have a lower level than the control signal S3 output from the filter 41.

In the switching power supply device having such a sudden load change detection circuit 60, both the operation of the switching power supply device shown in FIG. 1 and the operation of the switching power supply device shown in FIG. 4 can be obtained. That is, when the output voltage Vo drops sharply due to a sudden change in the load state, the control signal S4 output from the comparator 42 is output.
Is activated (becomes high level), the control signal S1
Of the control signal S7, which is the output of the comparator 52, is activated (becomes low level) when the output voltage Vo sharply rises due to a sudden change in the load state. Therefore, the level of the control signal S1 can be rapidly reduced. Further, in the normal state, the sudden load change detection circuit 60 operates as follows.
Has virtually no effect on the behavior of.

Therefore, in the switching power supply device according to this embodiment, it is possible to quickly recover the rapid decrease and increase in the output voltage Vo due to the sudden change in the load state. Therefore, for example, as a load, CPU or DS
When driving P, these malfunctions due to fluctuations in the power supply voltage that occur when the CPU or DSP switches from the active state to the inactive state or when switching from the inactive state to the active state are effectively prevented. can do.

Next, still another preferred embodiment of the present invention will be described.

FIG. 8 is a circuit diagram of a switching power supply device according to still another preferred embodiment of the present invention.

As shown in FIG. 8, the switching power supply device according to this embodiment is different from the switching power supply device shown in FIG. 1 in that the sudden load change detection circuit 7 is replaced by the sudden load change detection circuit 70. different. Since other configurations are similar to those of the switching power supply device shown in FIG. 1, duplicated description will be omitted.

The sudden load change detection circuit 70 includes a filter 71.
A filter 72, an operational amplifier 73, a comparator 74, a transistor 75, and resistors 76 to 80.

The filter 71 includes a pair of output terminals 3 and 4
It has resistors 81 and 82 connected in series between them and a capacitor 83 connected in parallel to the resistor 82, and the potential at the connection point of the resistors 81 and 82 is the control signal S9.
Used as. The filter 72 has a pair of output terminals 3
And 4 are provided with resistors 84 and 85 connected in series, and a capacitor 86 connected in parallel to the resistor 85, and the potential at the connection point between the resistors 84 and 85 is used as the control signal S10. . With this configuration, the filter 71 functions as a low-pass filter circuit that receives the output voltage Vo and outputs the control signal S9, and the filter 72
Functions as a low-pass filter circuit that receives the output voltage Vo and outputs the control signal S10.

Here, the characteristics of the filter 71 and the filter 7
The two filter characteristics are different from each other. More specifically, more specifically, the filter 71 is the filter 72.
The time constant is set to be larger than that. Therefore, when the output voltage Vo changes, the filter 72 changes more than the filter 71. When the output voltage Vo is stable, the control signal S9 output from the filter 71 and the control signal S10 output from the filter 72 are set to have substantially the same level. The setting of such characteristics is performed by the filters 71 and 7
2, resistors 81, 82, 84 and 85, and
This can be done by properly selecting the constants of the capacitors 83 and 86.

The operational amplifier 73 has an inverting input terminal (−), a non-inverting input terminal (+) and an output terminal, and a resistor 76 is connected between the inverting input terminal (−) and the filter 72.
A resistor 77 is connected between the inverting input terminal (−) and the output terminal. As a result, the operational amplifier 73 functions as an inverting amplifier whose amplification factor is determined by the ratio of the resistance value of the resistor 76 and the resistance value of the resistor 77. Here, the control signal S9 is supplied to the non-inverting input terminal (+) and the control signal S10 is supplied to the inverting input terminal (−) of the operational amplifier 73. As a result, the lower the level of the control signal S10 is compared to the level of the control signal S9, the higher the level of the control signal S11 which is the output of the operational amplifier 73.

The comparator 74 has an inverting input terminal (-),
The non-inverting input terminal (+) and the output terminal are provided, the control signal S11 is supplied to the non-inverting input terminal (+), and the output voltage Vo is divided by the resistors 78 and 79 at the inverting input terminal (-). The supplied voltage Vo1 is supplied. Accordingly, when the level of the control signal S11 is lower than the level of the voltage Vo1, the control signal S1 output from the comparator 74 is output.
2 becomes low level, and conversely, when the level of the control signal S11 is higher than the level of the voltage Vo1, the control signal S12 which is the output of the comparator 74 becomes high level. Although not shown in FIG. 8, it is preferable to add a capacitor in parallel with the resistor 79 in order to stabilize the voltage Vo1. Here, the control signal S12
Is used as a sudden load change detection signal.

Although not particularly limited, the transistor 75 is an NPN type bipolar transistor, and the control signal S12 is supplied to its base. The emitter of the transistor 75 is connected to the output terminal 4 (GN
D), and the collector of the transistor 75 is connected to the inverting input terminal (−) of the amplifier 30 via the resistor 80.

Next, the operation of the switching power supply according to this embodiment in the sudden load change state will be described.

FIG. 9 is a timing chart showing the operation of the switching power supply according to this embodiment in the sudden load change state. FIG. 9 shows the operation of the switching power supply device when the amount of the output current Io sharply increases from the time t20 to the time t22.

Before time t20, the output voltage Vo maintains the target voltage because the amount of the output current Io is small and there is almost no fluctuation. In this case, the control signal S9 output from the filter 71 and the control signal S10 output from the filter 72 are substantially equal in level, and the control signal S11 output from the operational amplifier 73 is substantially equal.
Is stable at a given level. Here, the predetermined level is lower than the voltage Vo1 obtained by dividing the output voltage Vo by the resistors 78 and 79, as shown in FIG. 9, and therefore the control signal S12 output from the comparator 74 is Keep low level. As a result, the transistor 75 is turned off, and the control signal S13 is in a high impedance state when viewed from the inverting input terminal (-) of the amplifier 30. Therefore, before the time t20, the sudden load change detection circuit 70 does not substantially affect the operation of the control circuit 6. In this case, the transfer function of the control circuit 6 has the first value, and the transfer function of the closed loop including the main circuit unit 5 and the control circuit 6 is suppressed to a value at which the output voltage Vo does not oscillate.

Next, when the output current Io starts to increase sharply at time t20, the output voltage Vo starts to decrease sharply. When the output voltage Vo drops sharply, the filter 71 that receives it drops the level of the output control signal S9, and the filter 72 drops the level of the output control signal S10. In this case, the control signal S10, which is the output of the filter 72, is set to fluctuate more than the control signal S9, which is the output of the filter 71, with respect to the fluctuation of the output voltage Vo. Control signal S1 which is the output of 73
The level of 1 rises according to these differences, and exceeds the voltage Vo1 at time t21.

As a result, the control signal S12 which is the output of the comparator 74 becomes high level, and the transistor 7
5 is turned on. When the transistor 75 is turned on, the level of the control signal S13 changes to the output terminal 4 (GND).
Therefore, the ground potential is supplied to the inverting input terminal (−) of the amplifier 30 via the resistor 80.

As a result, the level of the control signal S1 which is the output of the amplifier 30 rises rapidly and typically rises to the saturation level. Therefore, P that receives the control signal S1
The WM control circuit 31 substantially expands the pulse width of the output control signals a and b to the maximum value, whereby the lowered level of the output voltage Vo rapidly rises toward the target voltage. start. In such a state, the transfer function of the control circuit 6 has a second value exceeding the first value.
In this case, the transfer function of the closed loop including the main circuit unit 5 and the control circuit 6 may be at a level at which the output voltage Vo oscillates. Such a state is maintained until the level of the control signal S11 output from the operational amplifier 73 falls below the voltage Vo1 again.

The voltage Vo1 is, of course, the output voltage V
Although it changes in conjunction with o, the state of the fluctuation of the output voltage Vo is shown enlarged in FIG. 9, and therefore, the state of the fluctuation of the voltage Vo1 accompanying the fluctuation of the output voltage Vo is shown in FIG. Omitted.

Then, at time t23, the control signal S1
When the level of 1 falls below the voltage Vo1 again, the control signal S12 which is the output of the comparator 74 returns to the low level,
The transistor 75 is turned off again. This allows
The sudden load change detection circuit 70 has substantially no influence on the operation of the control circuit 6.

With the above operation, also in the switching power supply device according to the present embodiment, the rapid decrease in the output voltage Vo due to the sudden change in the load state can be quickly recovered, and the transient response is greatly improved.

Although various waveforms when the load sudden change detection circuit 70 is removed from the switching power supply device according to the present embodiment are not shown in FIG. 9, they are the same as those of the switching power supply device according to each of the embodiments described above. If the load sudden change detection circuit 70 is deleted, the output voltage V changes due to the sudden change in the load state.
Even if o decreases rapidly, the control signal S1 gradually increases, so that it takes a long time for the level of the output voltage Vo to return to the target voltage.

In the normal state, the output voltage Vo
Is small, the level of the control signal S11 output from the operational amplifier 73 does not exceed the voltage Vo1 and exceed. Therefore, in the normal state, the control signal S12, which is the output of the comparator 74, maintains the low level, and the transistor 75 maintains the off state. As described above, when the transistor 75 is in the off state, the sudden load change detection circuit 70 does not substantially affect the operation of the control circuit 6. Therefore, the switching power supply device according to the present embodiment can perform normal operation in the normal state.

As described above, in the switching power supply device according to the present embodiment, it is possible to quickly recover the rapid decrease in the output voltage Vo due to the sudden change in the load state.
Even when driving, the malfunctions due to the fluctuation of the power supply voltage can be effectively prevented.

Further, in the switching power supply device according to this embodiment, the level of the control signal S9 which is the output of the filter 71 and the control signal S which is the output of the filter 72 are provided.
The difference from the level of 10 is amplified by the operational amplifier 73 to generate the control signal S11, which is compared with the threshold voltage Vo1. It is possible to detect the sudden load change state with high accuracy and stability.

Further, in the switching power supply device according to the present embodiment, the threshold voltage Vo1 is generated based on the output voltage Vo, so that the output voltage setting VID (Voltage Identifier) is set.
output voltage Vo according to the control code and droop control.
Even when the target voltage is changed, the voltage Vo1 can be made to automatically follow the change in the level of the control signal S11 accompanying this. Therefore, even if the target voltage of the output voltage Vo is changed, it is not necessary to change the control in the sudden load change detection circuit 70.

Next, still another preferred embodiment of the present invention will be described.

FIG. 10 is a circuit diagram of a switching power supply device according to still another preferred embodiment of the present invention.

As shown in FIG. 10, the switching power supply device according to this embodiment is different from the switching power supply device shown in FIG. 1 in that the sudden load change detection circuit 7 is replaced by the sudden load change detection circuit 90. different. Since other configurations are similar to those of the switching power supply device shown in FIG. 1, duplicated description will be omitted.

The sudden load change detection circuit 90 has a structure similar to that of the sudden load change detection circuit 70 shown in FIG. 8. Compared with the sudden load change detection circuit 70, the comparator 74 is replaced by the comparator 91, and the transistor 75. Is replaced with a transistor 92, and resistors 78 to 80 are resistors 93 to
It is different in that it is replaced with 95. Other configurations are the same as those of the sudden load change detection circuit 70 shown in FIG. 8, and thus duplicated description will be omitted.

The comparator 91 has an inverting input terminal (-),
It has a non-inverting input terminal (+) and an output terminal, the control signal S11 is supplied to the non-inverting input terminal (+), and the output voltage Vo is divided by the resistors 93 and 94 at the inverting input terminal (-). The supplied voltage Vo2 is supplied. Accordingly, when the level of the control signal S11 is higher than the level of the voltage Vo2, the control signal S1 output from the comparator 91 is output.
4 becomes the high level, and conversely, when the level of the control signal S11 is lower than the level of the voltage Vo2, the control signal S14 which is the output of the comparator 91 becomes the low level. Although not shown in FIG. 10, it is preferable to add a capacitor in parallel with the resistor 94 in order to stabilize the voltage Vo2. Here, the control signal S1
4 is used as a load sudden change detection signal.

Although not particularly limited, the transistor 92 is formed of a PNP type bipolar transistor, and the control signal S14 is supplied to its base. The emitter of the transistor 92 is the output terminal 3 (Vo).
The collector of the transistor 92 is connected to the inverting input terminal (−) of the amplifier 30 via the resistor 95.

Next, the operation of the switching power supply according to this embodiment in the sudden load change state will be described.

FIG. 11 is a timing chart showing the operation of the switching power supply according to this embodiment in the sudden load change state. FIG. 11 shows the operation of the switching power supply device when the amount of the output current Io sharply increases from the time t30 to the time t32.

Before the time t30, the output voltage Vo maintains the target voltage because the amount of the output current Io is large and there is almost no fluctuation. In this case, the control signal S9 output from the filter 71 and the control signal S10 output from the filter 72 are substantially equal in level, and the control signal S11 output from the operational amplifier 73 is substantially equal.
Is stable at a given level. Here, the predetermined level means resistors 93 and 94 as shown in FIG.
Therefore, the output voltage Vo is higher than the divided voltage Vo2, and thus the control signal S14 which is the output of the comparator 91 maintains the high level. As a result, the transistor 92 is turned off, and the control signal S15 is in a high impedance state when viewed from the inverting input terminal (-) of the amplifier 30. Therefore, before the time t30, the sudden load change detection circuit 90 does not substantially affect the operation of the control circuit 6. In this case, the transfer function of the control circuit 6 has the first value, and the transfer function of the closed loop including the main circuit unit 5 and the control circuit 6 is suppressed to a value at which the output voltage Vo does not oscillate.

Next, when the output current Io starts to decrease sharply at time t30, the output voltage Vo starts to increase sharply. When the output voltage Vo rapidly rises, the filter 71 that receives it raises the level of the output control signal S9, and the filter 72 raises the level of the output control signal S10. In this case, the control signal S10, which is the output of the filter 72, is set to fluctuate more than the control signal S9, which is the output of the filter 71, with respect to the fluctuation of the output voltage Vo. Control signal S1 which is the output of 73
The level of 1 drops according to these differences, and falls below the voltage Vo2 at time t31.

As a result, the control signal S14 which is the output of the comparator 91 becomes low level, and the transistor 9
2 is turned on. When the transistor 92 is turned on, the level of the control signal S15 becomes the potential (power supply potential) of the output terminal 3 (Vo) , so that the inverting input terminal (−) of the amplifier 30 is connected to the power supply potential via the resistor 80. Is supplied.

As a result, the level of the control signal S1 which is the output of the amplifier 30 rapidly decreases, typically to the minimum level. Therefore, P that receives the control signal S1
The WM control circuit 31 narrows the pulse width of the output control signals a and b to a substantially minimum value, whereby the level of the output voltage Vo that has risen drops rapidly toward the target voltage. start. In such a state, the transfer function of the control circuit 6 has a second value exceeding the first value.
In this case, the transfer function of the closed loop including the main circuit unit 5 and the control circuit 6 may be at a level at which the output voltage Vo oscillates. Such a state is maintained until the level of the control signal S11, which is the output of the operational amplifier 73, exceeds the voltage Vo2 again and exceeds it.

Then, at time t33, the control signal S1
When the level of 1 again exceeds and exceeds the voltage Vo2, the control signal S14 which is the output of the comparator 91 returns to the high level, and the transistor 92 is turned off again. As a result, the sudden load change detection circuit 90 does not substantially affect the operation of the control circuit 6.

With the above operation, also in the switching power supply device according to the present embodiment, the rapid rise of the output voltage Vo due to the sudden change of the load state can be quickly recovered, so that the transient response is greatly improved.

Note that FIG. 11 does not show various waveforms when the sudden load change detection circuit 90 is removed from the switching power supply device according to the present embodiment, but it is similar to the switching power supply device according to each of the embodiments described above. By removing the sudden load change detection circuit 90, even if the output voltage Vo rapidly rises due to a sudden change in the load state, the control signal S1 gradually decreases, so that the level of the output voltage Vo returns to the target voltage. It takes a long time.

In the normal state, the output voltage Vo
Is small, the level of the control signal S11, which is the output of the operational amplifier 73, does not exceed the voltage Vo2 and fall below it. Therefore, in the normal state, the control signal S14 which is the output of the comparator 91 maintains the high level, and the transistor 92 maintains the off state. As described above, when the transistor 92 is in the off state, the sudden load change detection circuit 90 does not substantially affect the operation of the control circuit 6. Therefore, the switching power supply device according to the present embodiment can perform normal operation in the normal state.

As described above, in the switching power supply device according to the present embodiment, a rapid increase in the output voltage Vo due to a sudden change in the load state can be quickly recovered, so that, for example, a CPU or DSP as a load can be used.
Even when driving, the malfunctions due to the fluctuation of the power supply voltage can be effectively prevented.

Further, also in the switching power supply device according to this embodiment, the level of the control signal S9 which is the output of the filter 71 and the level of the control signal S10 which is the output of the filter 72 are the same as in the switching power supply device shown in FIG. The difference between the above and the voltage is amplified by the operational amplifier 73 to generate the control signal S11 and compared with the voltage Vo2 which is the threshold value. Therefore, it is more accurate than the switching power supply device shown in FIG. The sudden load change state can be detected stably.

Further, also in the switching power supply device according to this embodiment, the voltage Vo2 which becomes the threshold value is changed to the output voltage Vo, as in the switching power supply device shown in FIG.
Since it is generated based on the
Even if the target voltage of the output voltage Vo is changed by the D code or droop control, the control signal S
The voltage Vo2 can be made to automatically follow the change in the level of 11. Therefore, even if the target voltage of the output voltage Vo is changed, it is not necessary to change the control in the sudden load change detection circuit 90.

Next, still another preferred embodiment of the present invention will be described.

FIG. 12 is a circuit diagram of a switching power supply device according to still another preferred embodiment of the present invention.

As shown in FIG. 12, the switching power supply device according to this embodiment is different from the switching power supply device shown in FIG. 1 in that the sudden load change detection circuit 7 is replaced by the sudden load change detection circuit 100. different. Since other configurations are similar to those of the switching power supply device shown in FIG. 1, duplicated description will be omitted.

The sudden load change detection circuit 100 includes a filter 71.
The filter 72, the operational amplifier 73, the comparator 74, the comparator 91, the transistor 75, the transistor 92, and the resistors 76 to 80 and 93 to 95.

The circuit configurations of the filters 71 and 72 are as described above, and generate the control signals S9 and S10, respectively. The operational amplifier 73 also controls the control signal S as described above.
9 and S10 are received to generate a control signal S11 which is a signal obtained by amplifying the difference between these levels. Further, the comparators 74 and 91 also control the control signal S based on the control signal S11 and the corresponding voltage Vo1 or Vo2 as described above.
12 and S14 are generated respectively. Further, as described above, the transistor 75 is also supplied with the control signal S12 at its base, and its collector is connected to the inverting input terminal (−) of the amplifier 30 via the resistor 80. Similarly, the control signal S14 is supplied to the base of the transistor 92, and the collector of the transistor 92 is connected to the inverting input terminal (−) of the amplifier 30 via the resistor 95.

Further, as described above, the voltage Vo1 is higher than the level of the control signal S11 in the steady state, and
The voltage Vo2 is set to be lower than the level of the control signal S11 in the steady state.

In the switching power supply device having such a sudden load change detection circuit 100, both the operation of the switching power supply device shown in FIG. 8 and the operation of the switching power supply device shown in FIG. 10 can be obtained. That is,
That is, when the output voltage Vo sharply drops due to a sudden change in the load state, the control signal S12, which is the output of the comparator 74, is activated (becomes a high level), so that the level of the control signal S1 is rapidly increased. On the other hand, when the output voltage Vo sharply rises due to a sudden change in the load state, the control signal S14, which is the output of the comparator 91, is activated (becomes low level), so the control signal The level of S1 can be reduced rapidly. Further, in the normal state, the sudden load change detection circuit 100 has substantially no influence on the operation of the control circuit 6.

Therefore, in the switching power supply device according to the present embodiment, it is possible to quickly recover the rapid decrease and increase of the output voltage Vo due to the sudden change of the load state. Therefore, for example, as a load, CPU or DS
When driving P, these malfunctions due to fluctuations in the power supply voltage that occur when the CPU or DSP switches from the active state to the inactive state or when switching from the inactive state to the active state are effectively prevented. can do.

Next, still another preferred embodiment of the present invention will be described.

FIG. 13 is a circuit diagram of a switching power supply device according to still another preferred embodiment of the present invention.

As shown in FIG. 13, the switching power supply device according to this embodiment is different from the switching power supply device shown in FIG. 1 in that the sudden load change detection circuit 7 is replaced by the sudden load change detection circuit 110. different. Since other configurations are similar to those of the switching power supply device shown in FIG. 1, duplicated description will be omitted.

The sudden load change detection circuit 110 has a structure similar to that of the sudden load change detection circuit 70 shown in FIG. 8. In comparison with the sudden load change detection circuit 70, the comparator 74 is replaced with three comparators 111 to 113. Transistor 75 is replaced by three transistors 114-116, and a series body of resistors 78 and 79 forms a resistor 117.
It is replaced with a series body consisting of ~ 120, and the resistance 80 is 3
It is different in that it is replaced with one resistor 121 to 123. Other configurations are the same as those of the sudden load change detection circuit 70 shown in FIG. 8, and thus duplicated description will be omitted.

The comparator 111 has an inverting input terminal (-), a non-inverting input terminal (+) and an output terminal,
The control signal S11 is supplied to the non-inverting input terminal (+), and the voltage Vo3 obtained by dividing the output voltage Vo by the resistors 117 to 119 and the resistance 120 is supplied to the inverting input terminal (−). As a result, the level of the control signal S11 changes to the voltage V
If it is higher than the level of o3, the comparator 111
The control signal S16, which is the output of the control signal S16, becomes high level, and conversely, when the level of the control signal S11 is lower than the level of the voltage Vo3, the control signal S16 which is the output of the comparator 111 becomes low level.

The comparator 112 has an inverting input terminal (-), a non-inverting input terminal (+) and an output terminal,
The control signal S11 is supplied to the non-inverting input terminal (+), and the resistors 117 and 118 and the resistor 119 are supplied to the inverting input terminal (-).
And a voltage Vo obtained by dividing the output voltage Vo by 120 and 120.
4 is being supplied. Accordingly, when the level of the control signal S11 is higher than the level of the voltage Vo4, the control signal S17 which is the output of the comparator 112 becomes the high level, and conversely, the level of the control signal S11 is lower than the level of the voltage Vo4. In this case, the control signal S17 output from the comparator 112 becomes low level.

Further, the comparator 113 has an inverting input terminal (-), a non-inverting input terminal (+) and an output terminal. The control signal S11 is supplied to the non-inverting input terminal (+) and the inverting input terminal is supplied. The resistor 117 and the resistors 118 to 1 are included in (-).
A voltage Vo5 obtained by dividing the output voltage Vo by 20 is supplied. Thereby, when the level of the control signal S11 is higher than the level of the voltage Vo5, the control signal S18 which is the output of the comparator 113 becomes the high level, and conversely, the level of the control signal S11 is lower than the level of the voltage Vo5. In this case, the control signal S18 which is the output of the comparator 113 becomes low level.

Although not particularly limited, the transistor 114 is formed of an NPN type bipolar transistor, and the control signal S16 is supplied to its base. The emitter of the transistor 114 has an output terminal 4 (GN
D), and the collector of the transistor 114 is connected to the inverting input terminal (−) of the amplifier 30 via the resistor 121.

Although not particularly limited, the transistor 115 is formed of an NPN type bipolar transistor, and the control signal S17 is supplied to its base. The emitter of the transistor 115 is the output terminal 4
(GND), and the collector of the transistor 115 is connected to the inverting input terminal (−) of the amplifier 30 via the resistor 122.

Further, the transistor 116 is composed of an NPN type bipolar transistor, although not particularly limited, and the control signal S18 is supplied to its base. The emitter of the transistor 116 is connected to the output terminal 4 (GND), and the collector of the transistor 116 is connected to the inverting input terminal (−) of the amplifier 30 via the resistor 123.

The resistance values of the resistors 121 to 123 are set so that the combined resistance value when these are connected in parallel is about the same as the resistances 35, 54, 80 and 95 used in the above-described embodiments. Is desirable.

Although not shown in FIG. 13, in order to make the voltages Vo3 to Vo5 more stable, the resistor 120 is used.
It is preferable to add a capacitor in parallel with.

In the load sudden change detection circuit 110 having such a configuration, the relationship between the voltages Vo3, Vo4 and Vo5 is Vo3 <Vo4 <Vo5.
When the output voltage Vo drops due to a sudden change in the load state, the resistance value between the inverting input terminal (−) of the amplifier 30 and the output terminal 4 (GND) is changed stepwise according to the degree of the drop. You can

More specifically, when the level of the control signal S11, which is the output of the operational amplifier 73, is S11 <Vo3 (steady state), all the transistors 114 to 116 are turned off. When viewed from the inverting input terminal (-) of 30, the control signals S19 to S21 are in a high impedance state. Therefore, in this case, the sudden load change detection circuit 110 does not substantially affect the operation of the control circuit 6. In this case, the transfer function of the control circuit 6 has the first value, and the transfer function of the closed loop including the main circuit unit 5 and the control circuit 6 is suppressed to a value at which the output voltage Vo does not oscillate.

When the level of the control signal S11 output from the operational amplifier 73 is Vo3 <S11 <Vo4, the transistor 114 is turned on and the transistors 115 and 116 are turned off. The inverting input terminal (-) of 30 is supplied with the ground potential via the resistor 121. Therefore, the control signal S1 rises to the voltage level (V1) determined by the resistance value of the resistor 121. In such a state, the transfer function of the control circuit 6 has a second value exceeding the first value.

Further, when the level of the control signal S11 output from the operational amplifier 73 is Vo4 <S11 <Vo5, the transistors 114 and 115 are turned on and the transistor 116 is turned off.
The inverting input terminal (-) of the amplifier 30 is supplied with the ground potential via the parallel resistors 121 and 122. Therefore,
The control signal S1 is a voltage level (V2 (>) determined by a combined resistance value (first combined resistance value) of the parallel resistors 121 and 122.
V1)). In this case, since the first combined resistance value is lower than the resistance value of the resistor 121,
The control signal S1 rises when the level of the control signal S11 is Vo.
It is faster than the case of 3 <S11 <Vo4. In such a state, the transfer function of the control circuit 6 is the second
The third value exceeds the value of.

Further, when the level of the control signal S11 which is the output of the operational amplifier 73 is S11> Vo5, all the transistors 114 to 116 are turned on. Therefore, the inverting input terminal (-) of the amplifier 30 is turned on. Is supplied with the ground potential via the parallel resistors 121 to 123. Therefore, the control signal S1 has a voltage level (V) determined by the combined resistance value (second combined resistance value) of the parallel resistors 121 to 123.
3 (> V2)). In this case, since the second combined resistance value is lower than the first combined resistance value, the control signal S1 is increased more than when the level of the control signal S11 is Vo4 <S11 <Vo5. It will be prompt. In such a state, the transfer function of the control circuit 6 has a fourth value that exceeds the third value. In this case, the transfer function of the closed loop including the main circuit unit 5 and the control circuit 6 may be at a level at which the output voltage Vo oscillates.

As described above, in the switching power supply device according to the present embodiment, when the output voltage Vo drops due to a sudden change in the load state, the level of the control signal S1 rises to a voltage level corresponding to the degree of decrease of the output voltage Vo. Can be made. As a result, in the switching power supply device according to the present embodiment, it is possible to recover the output voltage Vo that has rapidly dropped due to a sudden change in the load state with higher accuracy than in the switching power supply device shown in FIG.

In the switching power supply device according to this embodiment, by using the three comparators 111 to 113, the recovery speed of the output voltage Vo which is rapidly lowered due to the sudden change of the load state is controlled in three stages. However, the number of comparators is merely an example, and two or four or more comparators may be used.

Although not shown, the comparator 74 included in the sudden load change detection circuit 70 shown in FIG.
In the same manner as the sudden load change detection circuit 110 shown in FIG. 3 is replaced with a plurality of comparators 111 to 113 having different threshold values, the comparator 91 included in the sudden load change detection circuit 90 shown in FIG. It may be replaced with a plurality of comparators having different threshold values.
By using such a load sudden change detection circuit, when the output voltage Vo rises due to a sudden change in the load state, the level of the control signal S1 can be lowered to a voltage level according to the degree of rise of the output voltage Vo. That is, it is possible to more accurately recover the output voltage Vo that rapidly rises due to a sudden change in the load state, as compared with the switching power supply device shown in FIG.

Further, although not shown, the comparator 74 included in the sudden load change detection circuit 100 shown in FIG. 12 is replaced with a plurality of comparators having different thresholds, and the comparator 91 is replaced with a plurality of thresholds different from each other. It may be replaced with a comparator. By using such a sudden load change detection circuit, when the output voltage Vo drops due to a sudden change in the load state, the level of the control signal S1 can be raised to a voltage level according to the degree of decrease of the output voltage Vo. When the output voltage Vo rises due to a sudden change in the load state, the level of the control signal S1 can be lowered to a voltage level according to the degree of rise of the output voltage Vo. That is, it is possible to recover the output voltage Vo, which is rapidly lowered or increased due to a sudden change in the load state, with higher accuracy than the switching power supply device shown in FIG. In this case, the number of comparators replacing the comparator 74 does not have to match the number of comparators replacing the comparator 91, and these numbers may be different from each other.

In the switching power supply device according to each of the embodiments described above, when the sudden load change state is detected by the sudden load change detection circuit, the level of the inverting input terminal (-) of the amplifier 30 included in the control circuit 6 is changed. The output voltage Vo is quickly recovered by controlling the output voltage Vo. However, in the present invention, this is a method for quickly recovering the output voltage Vo when the load sudden change detection circuit detects a sudden load change. The present invention is not limited to this, and other methods may be used to realize rapid recovery of the output voltage Vo.

FIG. 14 is a circuit diagram of the control circuit 130 included in the switching power supply according to still another preferred embodiment of the present invention.

As shown in FIG. 14, the control circuit 130
Includes a variable amplifier 131, a PWM control circuit 31, and an insulating circuit 32.

The variable amplifier 131 has an input end, an output end, and a control end (CONT). The output voltage Vo is applied to the input end, and the control end (CONT) detects the sudden load change shown in FIG. A control signal S4 from circuit 7 is applied.
The output from the output terminal of the variable amplifier 131 is used as the control signal S1. The gain of the variable amplifier 131 changes according to the level of the control signal S4 given to the control terminal (CONT). Specifically, the control end (CON
When the control signal S4 given to T) is at the low level, the gain of the variable amplifier 131 becomes the first gain (normal gain), and the control signal S4 given to the control end (CONT) is at the high level. The variable amplifier 13
The gain of 1 is the second gain which is higher than the first gain.

As described above, the control signal S4 is activated (high level) when the output voltage Vo drops rapidly due to a sudden change in the load state. Therefore, in the normal state, the gain of the variable amplifier 131 is the first. The gain becomes, and the gain of the variable amplifier 131 becomes the second gain in the sudden load change state. As a result, when the output voltage Vo drops rapidly due to a sudden change in the load state, the control signal S1 that is the output of the variable amplifier 131 rises quickly, and as in the switching power supply device shown in FIG. A rapid decrease in the output voltage Vo due to a sudden change can be quickly recovered.

The second gain of the variable amplifier 131 may be set to a high gain such that the closed loop transfer function of the main circuit section 5 and the control circuit 130 exceeds the limit value at which the output voltage Vo oscillates. I do not care. Variable amplifier 13
When 1 operates at such a high gain, the output voltage Vo eventually oscillates, but the control signal S4 is activated only for a short period in the sudden load change state. The voltage Vo never oscillates.

The control terminal (CON of the variable amplifier 131
The signal to be supplied to T) may be not only the control signal S4 but also the control signal S7, S12 or S14.

Further, when the control signals S16 to S18 that are generated stepwise according to the degree of change of the output voltage Vo are used as in the sudden load change detection circuit 110 shown in FIG. The gain is changed stepwise (control signal S16
It is preferable to use a variable amplifier that can be changed in four steps when using ~ S18.

Next, another method for promptly recovering the output voltage Vo will be described.

FIG. 15 is a circuit diagram of a control circuit 140 included in a switching power supply device according to still another preferred embodiment of the present invention.

As shown in FIG. 15, the control circuit 140
Are the first amplifier 141, the second amplifier 142, the first PWM control circuit 143, and the second PWM control circuit 1
44, a selector 145, and an insulating circuit 32.

In the control circuit 140, the gains of the first amplifier 141 and the second amplifier 142 are different from each other.
Specifically, the gain of the second amplifier 142 is set higher than the gain of the first amplifier 141. Also,
The first PWM control circuit 143 receives the control signal S1-1 which is the output from the first amplifier 141, controls the pulse widths of the control signals a1, b1, c1, d1 based on the control signal S1-1, and outputs the second PWM control circuit 143. The PWM control circuit 144 includes the second amplifier 14
The control signal S1-2 which is an output from the control signal 2 is received, and the pulse widths of the control signals a2, b2, c2 and d2 are controlled based on the control signal S1-2. These control signals a1, b1, c1, d1, a
2, b2, c2 and d2 are all supplied to the selector 145. The selector 145 includes a selection end (SELECT), and a control signal S4 given to the selection end (SELECT).
Is low level, the control signals a1, b1, c
1, d1 are selected and output, and conversely, the selection end (S
When the control signal S4 given to ELECT) is at a high level, the control signals a2, b2, c2 and d2 are selected and output.

As described above, the control signal S4 is activated (high level) when the output voltage Vo drops rapidly due to a sudden change in the load state. Therefore, in the normal state, the control signal a1, b1, c1, d1
Is selected, and the control signal a2, b2, c2, d2 is selected by the selector 145 in the sudden load change state.
As a result, when the output voltage Vo rapidly decreases due to a sudden change in the load state, it is possible to promptly recover the rapid decrease in the output voltage Vo due to the sudden change in the load state, as in the switching power supply device shown in FIG. it can.

Further, the gain of the second amplifier 142 may be set to a high gain such that the closed loop transfer function of the main circuit section 5 and the control circuit 140 exceeds the limit value at which the output voltage Vo oscillates. Absent. Furthermore, selector 1
The signal to be supplied to the selection terminal (SELECT) of 45 is not only the control signal S4 but also the control signal S7, S12 or S1.
It may be 4.

Further, when using the control signals S16 to S18 which are generated stepwise according to the degree of change of the output voltage Vo like the load sudden change detection circuit 110 shown in FIG. 13, the amplifier and the PWM control circuit are used. 3 sets or more (control signal S1
It is preferable to provide 4 sets when 6 to S18 are used.

Next, still another method for promptly recovering the output voltage Vo will be described.

FIG. 16 is a circuit diagram of a control circuit 150 included in a switching power supply device according to still another preferred embodiment of the present invention.

As shown in FIG. 16, the control circuit 150
Is a first amplifier 141, a second amplifier 142, a selector 151, a PWM control circuit 31, and an insulation circuit 32.
It has and.

The selector 151 has a selection terminal (SELEC
T) and the control signal S4 applied to the select terminal (SELECT) is at a low level, the first amplifier 1
The control signal S1-1 which is the output of 41 is selected and these are supplied to the PWM control circuit 31, and conversely, the selection end (SELE
When the control signal S4 applied to CT) is at a high level, the control signal S1 which is the output of the second amplifier 142
-1 is selected and these are supplied to the PWM control circuit 31.

As a result, the control circuit 150 can perform almost the same operation as the control circuit 140 described above.

Further, in the switching power supply device according to each of the embodiments described above, the low-pass filter circuit is used as the filter included in the sudden load change detection circuit. However, in the present invention, the filter included in the sudden load change detection circuit is used. Is not required to be a low pass filter,
As long as the time constants are set appropriately, these may be high-pass filters as shown in FIG.

Furthermore, in the switching power supply device according to each of the embodiments described above, a half-bridge type switching circuit is used as the primary side circuit of the main circuit section 5, and a current doubler is used as the secondary side circuit of the main circuit section 5. Although a type (double current type) output circuit is used, in the present invention, the primary side circuit and the secondary side circuit of the main circuit unit 5 are not limited to these, and other circuits may be used.

For example, a full bridge type circuit or a push-pull type circuit can be used as another primary side circuit applicable to the switching power supply device according to the present invention.
Further, as the other secondary side circuit applicable to the switching power supply device according to the present invention, a forward type circuit, a center tap type circuit, or a bridge type circuit can be used.

Further, in the switching power supply device according to each of the embodiments described above, the main circuit section 5 is
One transformer 10, one primary side circuit, one 2
Although a circuit including a secondary side circuit is used, in the present invention, a plurality of sets including a transformer, a primary side circuit, and a secondary side circuit may be used, and the phases may be shifted from each other and driven. Absent.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. It goes without saying that it is a thing.

For example, FIG. 8, FIG. 10, FIG. 12 and FIG.
In the switching power supply device shown in (1), for comparison with the level of the control signal S11 which is the output of the operational amplifier 73,
Voltage Vo1 to voltage V generated by dividing output voltage Vo
Although o5 is used, these voltages Vo1 to Vo5
Instead of, a predetermined reference voltage may be used. However, when a predetermined reference voltage is used instead of the voltages Vo1 to Vo5, and when the target voltage of the output voltage Vo is changed by the control circuit 6, it is necessary to change the level of the reference voltage accordingly. is there.

Further, in the switching power supply device according to each embodiment, the control circuits 6, 130, 140 and 1 are provided.
The output voltage Vo is directly supplied to the input terminals of the amplifiers 30, 141, 142 and the variable amplifier 131 included in 50. The input voltage is connected to the output voltage Vo, for example, a series of a plurality of resistors. Output voltage Vo using the body
It is also possible to supply a voltage obtained by dividing the voltage.

Further, in the switching power supply device according to each of the embodiments, the control circuits 6, 130, 140 and 150 all perform voltage mode control, but a control circuit for current mode control may be used. .

In addition, the control circuits 6, 130, 140 and 150 in the switching power supply device according to each embodiment.
Generates the control signal S1 which is an analog signal by using the amplifiers 30, 141, 142 and the variable amplifier 131, respectively, but these operations may be performed by digital signal processing.

Furthermore, the sudden load change detection circuit used in the switching power supply device according to each embodiment is an example of a circuit for detecting a sudden change in the load, and other circuits may be used to detect the sudden change in the load. Absent.

[0185]

As described above, according to the present invention,
The output voltage Vo decreases rapidly due to a sudden change in the load state and /
Alternatively, since the rise can be quickly recovered, it is possible to provide a switching power supply device in which transient response is significantly improved. As a result, according to the switching power supply device of the present invention, even when a load such as a CPU or a DSP whose load current changes rapidly is driven, these malfunctions can be effectively prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a switching power supply device according to a preferred embodiment of the present invention.

FIG. 2 is a timing diagram showing an operation of the switching power supply device shown in FIG. 1 in a sudden load change state.

FIG. 3 is a timing diagram showing an operation of the switching power supply device shown in FIG. 1 in a normal state.

FIG. 4 is a circuit diagram of a switching power supply device according to another preferred embodiment of the present invention.

5 is a timing diagram showing an operation of the switching power supply device shown in FIG. 4 in a sudden load change state.

FIG. 6 is a timing diagram showing an operation of the switching power supply device shown in FIG. 4 in a normal state.

FIG. 7 is a circuit diagram of a switching power supply device according to still another preferred embodiment of the present invention.

FIG. 8 is a circuit diagram of a switching power supply device according to still another preferred embodiment of the present invention.

9 is a timing chart showing an operation of the switching power supply device shown in FIG. 8 in a sudden load change state.

FIG. 10 is a circuit diagram of a switching power supply device according to still another preferred embodiment of the present invention.

11 is a timing chart showing an operation of the switching power supply device shown in FIG. 10 in a sudden load change state.

FIG. 12 is a circuit diagram of a switching power supply device according to still another preferred embodiment of the present invention.

FIG. 13 is a circuit diagram of a switching power supply device according to still another preferred embodiment of the present invention.

FIG. 14 is a circuit diagram of a control circuit 130 included in a switching power supply device according to still another preferred embodiment of the present invention.

FIG. 15 is a circuit diagram of a control circuit 140 included in a switching power supply device according to still another preferred embodiment of the present invention.

FIG. 16 is a circuit diagram of a control circuit 150 included in a switching power supply device according to still another preferred embodiment of the present invention.

FIG. 17 is a circuit diagram of a high pass filter.

[Explanation of symbols]

1,2 input terminals 3,4 output terminals 5 Main circuit section 6 control circuit 7 Load sudden change detection circuit 10 transformers 11 First input capacitor 12 Second input capacitor 13 First main switch 14 Second main switch 15,16,22,23 driver 17 First Reactor 18 Second Reactor 19 First rectifying switch 20 Second rectifying switch 21 Output capacitor 30 amplifier 31 PWM control circuit 32 insulation circuit 33-35 resistance 40, 41 filter 42 Comparator 43 transistor 44, 45, 47, 48 resistance 46,49 capacitors 50 Load sudden change detection circuit 51 filters 52 Comparator 53 transistor 54-56 resistance 57 Capacitor 60, 70 Load sudden change detection circuit 71,72 Filter 73 Operational amplifier 74 Comparator 75 transistor 76 to 82,84,85 resistance 83,86 capacitors 90 Load sudden change detection circuit 91 Comparator 92 transistor 93-95 resistance 100,110 Load sudden change detection circuit 111-113 Comparator 114-116 transistors 117-123 resistance 130 control circuit 131 Variable amplifier 140 control circuit 141 First Amplifier 142 Second amplifier 143 First PWM control circuit 144 Second PWM control circuit 145 selector 150 control circuit 151 selector

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-10-210741 (JP, A) JP-A-1-133568 (JP, A) JP-A-6-233530 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H02M 3/28

Claims (4)

(57) [Claims] 1. A main circuit section having a switching circuit for converting a direct current input voltage into an alternating voltage and an output circuit for rectifying the alternating voltage to generate a direct current output voltage, and the output voltage or interlocked therewith. A control circuit that has at least an amplifier that receives a voltage at the input end and that controls the operation of the main circuit section; and a load circuit supplied from the main circuit section that responds to a change at a speed exceeding a predetermined speed. A switching power supply device comprising means for varying the level of the input terminal of the amplifier. 2. The level of the input terminal of the amplifier that changes in response to the load current changing at a speed exceeding a predetermined speed is a level at which the output of the amplifier saturates. The switching power supply device according to claim 1. 3. The means unidirectionally fluctuates the level at the input end of the amplifier in response to the load current increasing at a rate above the predetermined rate, the load current being at the predetermined level. 3. The switching power supply device according to claim 1, wherein the level of the input end of the amplifier is changed in the opposite direction in response to the decrease at a speed exceeding the speed. 4. The second means comprises: a first level when the load current changes at a first speed that is equal to or lower than the predetermined speed, and a second level when the load current exceeds the predetermined speed.
4. The level of the input terminal of the amplifier is changed so as to reach a second level exceeding the first level when changing at a speed of 1. The switching power supply device according to.